If you're looking for a decent, inexpensive cordless mouse head on down to your local Staples store. They've currently got the Logitech M305 on sale for $19.99 + tax (Newegg normally sells 'em for around $30).

It comes in different colors, has a tilt-wheel for side scrolling, and runs for months on a single AA battery. The receiver is really tiny, which is great if you like to use a mouse with your laptop since the receiver doesn't get in the way. I also like it (and other similarly shaped mice) because I have small-ish hands and the M305 is slightly smaller than a standard mouse; people with larger hands might consider this a disadvantage however!

When I initially got to the store I thought they had a crappy selection of colors (only black), but that was because they didn't have most of them over in the mouse/keyboard aisle. They had their own display rack out in the main aisle, in all the colors...